In the NFL, there are many things players need to watch out for, as using banned items or substances can seriously impact their careers. The list is long, but here we have highlighted 43 of the most common reasons that have gotten players into trouble. Some of these rules even apply to spectators in the stadium. 1. Performance Enhancing Drugs (PEDs) In the 1987 season, the National Football League (NFL) started testing players for steroid use for the first time.